[analyzer] Suppress warnings coming out of macros defined in sys/queue.h

Suppress the warning by just not emitting the report. The sink node
would get generated, which is fine since we did reach a bad state.

Motivation

Due to the way code is structured in some of these macros, we do not
reason correctly about it and report false positives. Specifically, the
following loop reports a use-after-free. Because of the way the code is
structured inside of the macro, the analyzer assumes that the list can
have cycles, so you end up with use-after-free in the loop, that is
safely deleting elements of the list. (The user does not have a way to
teach the analyzer about shape of data structures.)

SLIST_FOREACH_SAFE(item, &ctx->example_list, example_le, tmpitem) {
			if (item->index == 3) { // if you remove each time, no complaints
				assert((&ctx->example_list)->slh_first == item);
				SLIST_REMOVE(&ctx->example_list, item, example_s, example_le);
				free(item);
			}
		}

llvm-svn: 172883

1 files changed, 25 insertions, 0 deletions

diff --git a/clang/lib/StaticAnalyzer/Core/BugReporter.cpp b/clang/lib/StaticAnalyzer/Core/BugReporter.cpp
index 8e6bc69cc4a..d64aa39febe 100644
--- a/clang/lib/StaticAnalyzer/Core/BugReporter.cpp
+++ b/clang/lib/StaticAnalyzer/Core/BugReporter.cpp
@@ -2137,7 +2137,32 @@ void BugReporter::Register(BugType *BT) {
   BugTypes = F.add(BugTypes, BT);
 }
 
+bool BugReporter::suppressReport(BugReport *R) {
+  const Stmt *S = R->getStmt();
+  if (!S)
+    return false;
+
+  // Here we suppress false positives coming from system macros. This list is
+  // based on known issues.
+
+  // Skip reports within the sys/queue.h macros as we do not have the ability to
+  // reason about data structure shapes.
+  SourceManager &SM = getSourceManager();
+  SourceLocation Loc = S->getLocStart();
+  while (Loc.isMacroID()) {
+    if (SM.isInSystemMacro(Loc) &&
+       (SM.getFilename(SM.getSpellingLoc(Loc)).endswith("sys/queue.h")))
+      return true;
+    Loc = SM.getSpellingLoc(Loc);
+  }
+
+  return false;
+}
+
 void BugReporter::emitReport(BugReport* R) {
+  if (suppressReport(R))
+    return;
+
   // Compute the bug report's hash to determine its equivalence class.
   llvm::FoldingSetNodeID ID;
   R->Profile(ID);